A camshaft adjuster serves for the targeted adjustment of the phase position between a camshaft and a crankshaft in an internal combustion engine and thus permits optimized setting of the valve timings. By this means, for example, the performance of an internal combustion engine can be increased or the consumption can be reduced.
A camshaft adjuster has a stator which is connected to the crankshaft for rotation therewith, and a rotor which is retained in said stator. The rotor is connected to the camshaft in turn for rotation therewith and can be adjusted with respect to the stator. The adjustment of the rotor is brought about by charging pressure chambers formed in the stator with a hydraulic fluid, such as oil. The charging is ensured via a pressure line communicating with the pressure side of the oil supply system. The oil is pumped here by means of a pump from an oil reservoir within the engine oil circuit via the pressure line into the pressure chambers of the camshaft adjuster and can therefore be used for adjusting the camshaft.
In the process, the oil may be contaminated with particles which arise, for example, due to abrasion of moving components during operation of the internal combustion engine. The contaminated oil may be transported via the control valve into the pressure chambers of the camshaft adjuster and may be deposited there. This may result in restricted operation or even to failure of the camshaft adjuster.
In order to prevent this, use is made of filter elements which extract particles from the oil prior to entry into the control valve or the pressure chambers. Filter elements customarily consist of a filter fabric retained within a frame. A filter element of this type is known from WO 2006/136258 A1. The filter element is formed integrally with a filter fabric and a frame and is positioned fixedly in an annular groove on a control valve. The filter fabric is cast into the frame during production of the latter. In other words, the filter fabric and the frame are connected fixedly to each other.
The drawback of this is, if the frame is damaged, the filter fabric is also damaged and therefore loses its filter effect. A cast filter fabric therefore does not constitute a permanent solution as a particle filter for a control valve.